This is a question from a very old AP Chem exam (2006) prep book which I am amusing myself with in my spare time which is kind of humbling. There is something I am missing with this question, one of several similar questions in the kinetics section.
Given the following reaction (which doesn't establish an equilibrium) :
$\ce{A (g) + B (g) -> C (g)}$
which of the following would increase the concentration of $\ce{A}$?
- addition of $\ce{A}$ at constant $T$ and $V$
- addition of $\ce{A}$ at constant $T$ and $P$
- addition of $\ce{A}$ at constant $V$ and $P$
Now my first thoughts are to reason as follows :
If you add $\ce{A}$ and the volume is constant obviously the concentration of $\ce{A}$ increases. If you add $\ce{A}$ and keep $T$ and $P$ constant the $V$ will just expand and the concentration will be the same. But if I ignore the reaction this is a gas law / concentration question so it is out of place. But it isn't an equilibrium so none of that reasoning applies either.
Now if the reaction happens so slow it takes a year for $1\,\%$ of $\ce{A}$ to react I could just consider the reaction not even happening? If the reaction happens so fast that it is essentially over in 1 second then it seems like any change to A would be undone as fast as you could increase it. But it seems like I am missing something basic as there is nothing given regarding the rate.
There are several questions almost identical to this in the same section which just have other than $1:1$ coefficients in the equation.